Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$99.97	11.479%	$111.4456	$111.45	$111.45	$111.40
Purchase #2	$5.87	11.114%	$6.5224	$6.52	$6.50	$6.50
Purchase #3	$195.96	10.106%	$215.7637	$215.76	$215.75	$215.80
Purchase #4	$117.29	8.751%	$127.554	$127.55	$127.55	$127.60
Purchase #5	$125.39	13.203%	$141.9452	$141.95	$141.95	$141.90
Purchase #6	$245.40	7.786%	$264.5068	$264.51	$264.50	$264.50
Purchase #7	$28.40	13.413%	$32.2093	$32.21	$32.20	$32.20
7 purchase totals =	$818.28		$899.9470	$899.95	$899.90	$899.90